There is known a liquid crystal lens device utilizing birefringence of liquid crystal molecules to change the distribution of refractive index in response to voltage application. There is known an image display device including the liquid crystal lens device combined with an image display unit. In this image display device, the distribution of refractive index of the liquid crystal optical element is changed to switch between two states. In the first state, the image displayed on the image display unit is made directly incident on the observer's eye. In the second state, the image displayed on the image display unit is made incident on the observer's eye as a plurality of parallax images. This realizes a two-dimensional image display operation and a three-dimensional image display operation. High display quality is desired in such an image display device. A high quality lens function is desired in the liquid crystal lens device.